Heavy duty vehicle redundant braking system

ABSTRACT

An electronically controlled pneumatic brake system for a vehicle, with a normal brake operating mode (NOM) and a backup brake operating mode (BKM), said system comprising: —a front axle brake module (FBM) for providing pneumatic control pressure to the left and right front pneumatic brake actuators (FW-L, FW-R), one or more rear axle brake module (RBM) for providing pneumatic control pressure to the left and right rear pneumatic brake actuators (RW-L,RW-R), a trailer brake interface(5), —an air production module (6) selectively providing air under pressure to said axles electronic brake modules (FBM,RBM) via first and second air supply circuits (AC1,AC2), a trailer relay valve (1), wherein each of the front and rear axle brake modules (FBM,RBM) is controlled by an electrical control signal (NBC,ES1,ES2) under the normal brake operating mode (NOM) and is controlled by a pneumatic backup brake control line (BKC) under the backup brake operating mode (BKM), wherein the output (12) of trailer relay valve is connected to the trailer brake interface(5) under the normal brake operating mode (NOM), and the output (12) of trailer relay valve is connected to the pneumatic backup brake control line (BKC) under the backup brake operating mode (BKM).

FIELD OF THE INVENTION

This invention relates to an electronically controlled pneumatic brakesystem for an automotive vehicle. This invention also relates to anautomotive vehicle equipped with such a system.

BACKGROUND OF THE DISCLOSURE

In the field of automotive vehicles, reliable trajectory control isamong the prominent safety features required for ensuring smooth andsecure traffic on roads. More particularly, steering and brakingfunctions are of utmost importance.

The present disclosure focuses more particularly on the brakingfunction, which relies, in particular for trucks, and more generally forheavy duty vehicles, on an electro-pneumatic system using air underpressure as working fluid.

It has been made compulsory for long to provide two independentpneumatic circuits, as a redundant arrangement in order to keep abraking capability in case one circuit undergoes a failure.

Later, solutions using electric control on top of baseline pneumaticsystem were introduced to speed up pressure changes at axles, so theeffective control at brake actuators can reflect driver controls in amore real time fashion.

More recently, a trend to go towards brake-by-wire solutions has leadthe trucks designers to simplify the foot pedal brake unit by removingall the pneumatic components from the foot pedal unit, as taught inEP2794368. However, reliability and tolerance to failure(s) must stillbe ensured, especially in the area of electrical controls and pneumaticcontrols.

Now, with the outlook of autonomous vehicles and vehicle automation, theinventors have endeavored to find new solutions for providing redundantelectro-pneumatic braking systems.

SUMMARY OF THE DISCLOSURE

According to one aspect of the present invention, it is disclosed anelectronically controlled pneumatic brake system for an automotivevehicle, said system being configured to operate either under a normalbrake operating mode (NOM) or under a backup brake operating mode (BKM),said system comprising:

-   -   one or more front axle brake module (FBM) for providing        pneumatic control pressure to the left and right front pneumatic        brake actuators (FW-L, FW-R),    -   one or more rear axle brake module (RBM) for providing pneumatic        control pressure to the left and right rear pneumatic brake        actuators (RW-L,RW-R),    -   a trailer brake interface (5) and a coupling device for        supplying air to a trailer (if/when coupled),    -   an air production module (6) selectively providing air under        pressure to said axles electronic brake modules (FBM,RBM) via at        least a first air supply circuit (AC1) and a second air supply        circuit (AC2), and to a trailer circuit,    -   at least two air reservoirs (R1,R2), respectively connected to        first and second air supply circuits,    -   a trailer relay valve (1), having an output (12),        wherein each of the front and rear axle brake modules (FBM,RBM)        is controlled by an electrical control signal (NBC,ES1,ES2)        under the normal brake operating mode (NOM) and is controlled by        a pneumatic backup brake control line (BKC) under the backup        brake operating mode (BKM), characterized in that        the output (12) of trailer relay valve is connected to the        trailer brake interface (5) under the normal brake operating        mode (NOM), and the output of trailer relay valve is connected        to the pneumatic backup brake control line (BKC) under the        backup brake operating mode (BKM).

Thanks to this arrangement, it is possible to optimize the overallconfiguration of the braking system, and to selectively use the trailerrelay valve and related components for two functions according to acurrent prevailing operating mode.

A relevant functional redundancy is therefore provided with fewadditional components in the pneumatic circuit.

By the term “trailer brake interface”, it shall be understood either atrailer brake valve as used in the European standard (ref 5 FIG. 1) or atractor protection valve as used in the US standard (ref 5′ FIG. 6).

In various embodiments of the invention, one may possibly use inaddition to one and/or other of the following arrangements, taken aloneor in combination.

According to one aspect, the system comprises:

-   -   a switchover auxiliary valve (2), for connecting selectively the        output (12) of the trailer relay valve (1) either to the trailer        brake interface (5) or to the a pneumatic backup brake control        line (BKC), depending on the current operating mode (NOM,BKM),        and controlled by at least:    -   a backup mode selection valve (3).

This forms a simple and reliable solution to swap from one configurationto another configuration.

According to one aspect, the switchover auxiliary valve (2) is a 4/2valve with four ports and two plunger positions, with a pneumaticcontrol. Thanks to this arrangement, the trailer can still be suppliedwith air under pressure, even though the normal pneumatic line has beenredirected to the truck brake backup control line.

According to one aspect, the backup mode selection valve (3) is anON/OFF electro-valve, with its output (32) connected to the pneumaticcontrol port (25) of the switchover auxiliary valve (2). Whereby theswitch from one mode to another is made simple and easy to control.

According to an alternative aspect, the system may comprise a select lowvalve (9) with its output (93) connected to the pneumatic control port(25) of the switchover auxiliary valve. Whereby, the behavior duringreset, during transient configurations, together with the defaultposition(s) improves the dependability rating of the system.

According to one aspect, one input port (92) of the select low valve (9)is supplied by the supply line (50) to the trailer brake interface (5),and the other input port (91) of the select low valve (9) is supplied bythe backup mode selection valve (3). Whereby, we make sure that thetrailer brake interface is first pressurized before the backup mode canbe activated, contributing to the reliability of the pneumatic backupbrake control line (BKC). Further this configuration allows preventingan inadvertent braking of the trailer.

According to one aspect, the backup mode selection valve (3) is anormally open valve. Whereby, under lack of power supply or lack ofcontrol, the switchover auxiliary valve is caused to be in the backupmode configuration.

According to an alternative solution, the backup mode selection valve(3) can be a normally closed valve. In this case, its output can controldirectly the switchover auxiliary valve (2). Thereby, only fewadditional components are required.

According to one aspect, the backup mode selection valve (3) iscontrolled by an air production module control unit (61) housed in theair production module (6). Thereby, no other unit external to the airproduction module is necessary to control the selection of the backupbrake operating mode (BKM). In the event brake control unit (73) and/orautonomous drive control units (71,72) fail, the air production module(6) can activate by its own the backup brake operating mode (BKM).

According to one aspect, the system may comprise a proportional trailercontrol solenoid valve (4), to provide a control pressure to the trailerrelay valve (1).

Advantageously, this solenoid valve is used for making available thepneumatic backup brake control line (BKC) under the backup brakeoperating mode. The solenoid valve is preferably a proportional valve tooutput any desired control pressure between zero and 12 bars (standardpressure level available at the reservoirs).

According to one aspect, the trailer control solenoid valve (4) iscontrolled by the air production module control unit (61) housed in theair production module (6). This control solenoid valve can be controlledin a proportional way such its output can be any controlled pressurebetween 0 and the brake service pressure (e.g. 12 bars).

According to one aspect, the system may comprise

-   -   a service brake electric input device (16) delivering a first        input electric signal (S16);    -   at least one electronic brake control unit (71,72,73) adapted to        process the first input electric signal, and to deliver        electrical control signals (NBC,ES1,ES2). Thereby, a        brake-by-wire configuration is made available, with a foot brake        pedal without any pneumatic component.

According to one aspect, at least one electronic brake control unit(71,72) is a vehicle autonomous drive control unit. The proposedredundant braking system opens many possibilities to practice safeautonomous drive.

According to one aspect, at the pneumatic backup brake control line(BKC) is output and controlled by the air production module (6),independently of the brake control unit (73) and/or autonomous drivecontrol units (71,72). Functional redundancy is thereby achieved.

According to one aspect, the system may further comprise a truck parkingbrake relay valve (8). The parking brake function which is integratedwithin the APM can also be used as an emergency braking fallback system,thereby improving the overall functional redundancy.

According to one aspect, the system may further comprise:

-   -   a truck parking brake relay valve (8),    -   a parking brake electric input device (18) delivering a second        input electric signal (S18),    -   an air production module control unit (61) adapted to process        the second input electric signal (S18), and to deliver control        signals to a proportional park brake control solenoid valve        (89), which provides a control pressure to the parking brake        relay valve (8). The parking brake function can also be used as        an emergency braking fallback system, thereby improving the        functional redundancy. The production module control unit (61)        is a common resource to the parking brake function and to the        backup pneumatic control (BKC).

According to an optional aspect, there may be provided with regard tothe USA standards, an additional braking handle (19) in relation withthe trailer brake control. Another way to apply brake to the trailer isthereby provided.

According to one aspect, the switchover auxiliary valve (2), the backupmode selection valve (3), and optionally the select low valve (9) arehoused within the air production module (6). The APM is an integratedand optimized unit, providing protection against mechanical and fluidsrisks.

According to one aspect, there is provided a third air supply circuit(AC3) for providing a redundant pneumatic supply to the front and rearaxle brake modules (FBM,RBM). Thereby, full redundancy is achieved, notonly regarding the control lines but also regarding the supply incompressed air via the redundant third circuit supply. More precisely,the system can withstand a substantive electric failure and asubstantive pneumatic failure while maintaining a full proportionalbraking capability on front and rear axles.

The invention is also directed to a vehicle including a brake system asdescribed above.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention appear from the followingdetailed description of two of its embodiments, given by way ofnon-limiting example, and with reference to the accompanying drawings,in which:

FIG. 1 illustrates a diagrammatical circuit layout of anelectro-pneumatic braking system for a truck according to the invention,

FIG. 2A shows a more detailed view of a particular portion of the airproduction module,

FIG. 2B is similar to FIG. 2A and shows a variant embodiment,

FIG. 3 illustrates an electrical and functional diagram,

FIG. 4 is similar to FIG. 1 and shows a variant embodiment,

FIG. 5A shows a more detailed view of the area of the trailer relayvalve under normal operating mode.

FIG. 5B is similar to FIG. 5A and shows the area of the trailer relayvalve under backup operating mode.

FIG. 6 illustrates a variant embodiment for the trailer interface,

FIG. 7 illustrates a pneumatic brake actuator.

DETAILED DESCRIPTION OF THE DISCLOSURE

In the figures, the same references denote identical or similarelements. Unless stated otherwise, the pneumatic lines are shown thickerthan the electrical lines.

FIG. 1 shows a diagrammatical circuit layout of an electro-pneumaticbraking system for a truck. The proposed configuration is also valid forany kind of heavy-duty vehicles including buses and coaches.

The truck considered here can be the traction unit in a tractor/trailerconfiguration or it can be a utility ‘carrier’ truck.

At least one front axle is a steering axle, without excluding otheraxle(s) having a steering function including a rear axle.

The truck considered here can have one or more level(s) of autonomousdrive functionalities, entailing reinforced needs for redundancy inbraking systems.

Overview of the Braking System

Here we describe the braking system from the wheel to the source. Forthe sake of clarity we have represented the same brake actuator for allthe wheels, but of course, there may be variations and differencesaccording to the location of the wheel (front, rear, trailer etc. . . .)

As known per se, all truck brakes actuators (RW-L, RW-R, FW-L, FW-R) canbe combined service brake and park brake actuators. As shown in FIG. 7each brake actuator (generically referred to as BA) includes a firstpiston 81 loaded by a first spring 82 which exerts a first effort E1 ina first direction D1. Brake actuator BA also includes a second piston 83loaded by a second spring 84 which exerts a second effort E2 in adirection D2 opposite to direction D1. Piston 83 is rigid with an outputrod 88 of brake actuator which drives an associated brake mechanism(brake pads, disc, etc. . . . not shown). A fixed wall 86 is mountedwithin a housing 87 of brake actuator. Wall 86 defines, respectivelywith pistons 81 and 83, two chambers C1, C2 of a variable volume. Therod 88 is coupled to the piston 83, crosses the wall 86 in an air tightmanner and is coupled to the piston 81. Springs 82 and 84 are chosen sothat effort E1 is larger than effort E2. Thus, in absence of airpressure within chambers C1 and C2, effort E1 pushes piston 81 indirection D1. This effort is transmitted by piston 83 to rod 88 toactuate the associated brake mechanism in a first direction. Under suchcircumstances, brake mechanism engages the brake disk(s) or drum(s) ofthe associated rear left wheel or wheels. This corresponds to a parkbrake actuation for truck. In other words, when no air under pressure isprovided to brake actuator BA, the park brake of truck is actuated.Instead of pistons, flexible membranes or diaphragms can be used.

When air under pressure is provided to chamber C1 supplied by input PBR(Parking Brake Release, respectively PBR2 or PBR1 for front and rear),the air pressure within this chamber pushes piston 81 against the actionof spring 82 and spring 84 pushes piston 83 in direction D2. Thiscorresponds to the release of the park brake of truck by air pressure.

When the park brake has been released and if air under pressure isprovided to chamber C2 supplied by input BC (Brake control), the airpressure within chamber C2 pushes piston 83 in direction D1 whichprogressively actuates brake mechanism in order to brake thecorresponding wheel or wheels. The mechanical effort delivered by theactuator to the brake mechanism increases with the air pressuredelivered to chamber C2. This corresponds to the actuation of theservice brake of truck. The service brake actuator is the device whichtransforms the air pressure into a mechanical force.

Trailer brake actuator can be similar to truck brake actuator (suppliedby PBR3 for parking brake).

There may be provided more than 4 brake actuators, in case there are twofront axles, and/or two or more rear axles. The number of brakeactuators can amount to 2,4,6,8, or more. It is worth noting that somebrake actuators can be deprived of the parking brake function. Thenumber of brake actuators can be twice the number of axles.

In the illustrated example, each axle or group of axles is equipped witha brake module, e.g. in the illustrated example a front axle brakemodule FBM and one (or more) rear axle brake module RBM.

However, in other configurations (not shown), there may be provided onesuch brake module per wheel or one such brake module per twin wheels.

The front axle brake module FBM provides pneumatic control pressure tothe left and right front pneumatic brake actuators (FW-L, FW-R). Therear axle brake module RBM provides pneumatic control pressure to theleft and right rear pneumatic brake actuators (RW-L,RW-R).

Each of the front and rear axle brake modules (FBM,RBM) is anelectro-pneumatic device, known per se, providing a pneumatic relayfunction. In short, it selectively takes air from the compressed airsupply and selectively releases air to the atmosphere while followingfaithfully the control signals (electrical and/or pneumatic); its outputis connected to the chamber C2 of the corresponding brake actuator BA.

There are provided a first air supply circuit AC1 and a second airsupply circuit AC2.

There is provided a first air reservoir R1 coupled to the first airsupply circuit AC1.

There is provided a second air reservoir R2 coupled to the second airsupply circuit AC2.

Said otherwise, there are provided two air reservoirs (R1,R2, alsocalled ‘vessels’), respectively connected to first and second air supplycircuits (AC1,AC2), which are designed to be independent from oneanother. First and second air supply circuits AC1,AC2, have a servicepressure set around 12 bars. In practice, first and second air supplycircuits AC1,AC2, may have a service pressure comprised in the range [5bars-15 bars], preferably comprised in the range [7 bars-12 bars].

The first air supply circuit AC1 provides air under pressure to the rearaxle brake module RBM. The second air supply circuit AC2 provides airunder pressure to the front axle brake module FBM. AC1 is sometimescalled ‘primary’ circuit, AC2 is sometimes called ‘secondary’ circuit,since rear brakes are usually more powerful than front brakes.

There is provided an air compressor 60, for compressing air taken fromthe environment; the output of the compressor goes through afilter/dryer 62; These components are known per se thus not described indetail here.

There are provided here various control units, namely a ‘conventional’brake control unit 73, and one or two autonomous drive ECUs 71,72.

As apparent from FIG. 1 and FIG. 4, each of the front and rear axlebrake modules FBM,RBM can be either in one integrated unit or in 3physical units, with the PCV (pressure control valve) separated from thepneumatic relay function.

The PCV (pressure control valve) performs anti-locking function (ABSfunction). PCV has a first valve in a series arrangement that can blockthe passage or air down to the brake chamber, and a second valve thatcan take out air from the brake chamber circuit and release it to theatmosphere. These valves are controlled in accordance with the real timeanalysis of the speed of each wheel.

As shown in FIG. 1, the PCV (pressure control valve) are separated fromthe FBM which performs mainly a relay function (electrical+pneumaticcontrol for this relay function).

As shown in FIG. 4, the PCV (pressure control valve) are integrated inthe FBM and RBM respectively. Of course mixed configuration is possible.

There are provided wheel speed sensors WSS, at least one per brakedwheel. Four are shown at the figures, but having more wheel speedsensors is possible.

The signals from the wheel speed sensors WSS are analyzed at one or morecontrol unit which delivers output signals to control the valves of therespective PCV (pressure control valve). The control unit in charge ofABS regulation can be a local control unit within the front and rearaxle brake modules FBM,RBM; it can also be the conventional brakecontrol unit 73; it can also be one or both of the autonomous drive ECUs71,72.

APM/EPB and its Relay Valves and Other Ancillaries

There is provided an air production module 6 (‘APM’ in short),preferably housing components inside a protective enclosure, therebyproviding protection against mechanical and fluid attacks. The airproduction module 6 is located behind the cabin, accessible from oneside of the truck for carrier type truck, or accessible from top sideif/when the cabin is tilted or rocked. The air production module 6 maycomprise various valves, solenoids, relay valves, pressure sensor and acontrol unit 61.

The air production module 6 houses the core of the parking brakefunction and comprises the truck PBR relay valve 8. As known per se,there is provided a parking brake electric input device 18 outputting anelectric signal S18, which is delivered to the control unit 61 of theAPM 6.

The control unit 61 of the APM 6 delivers in turn an appropriate signalto control a proportional park brake control solenoid valve 89 housed inthe APM, which provides a control pressure to the parking brake relayvalve 8.

There may be provided, with regard to the USA standard, an additionalbraking handle 19 (‘red knob’) in relation with the trailer brakecontrol. A corresponding electric signal S19 is delivered to the controlunit 61 of the APM 6.

For the air under pressure PP, coming from the compressor and filter,there is provided a trunk portion AC0. The trunk portion AC0 distributesair through overflow valves (not shown) to first and second air supplycircuits AC1, AC2, and optionally to a third air supply circuit AC3. Thethird air supply circuit AC3 provides a redundant air supply to thefront and rear axle brake modules FBM, RBM. AC3 is shown in dotted linein FIG. 1.

For the front section, a first double check valve 20F is arranged at thevicinity or within the front axle brake module FBM. FBM is supplied bythe higher pressure of AC2 or AC3. For the rear section, a first doublecheck valve 20R is arranged at the vicinity or within the rear axlebrake module RBM. RBM is supplied by the higher pressure of AC1 or AC3.

However, the third air supply circuit is not compulsory, FIG. 4illustrates a configuration with only the primary and secondary aircircuits AC1, AC2.

Additionally, the trunk portion AC0 distributes air through an overflowvalve to another air supply circuit denoted AC4 for supplying the truckPBR relay valve 8 and a trailer relay valve 1. Optionally, there may beprovided another air supply circuit denoted AC5 for supplying the airsuspension system and possibly other truck ancillaries. In addition, theair production module 6 may comprise various simple or double checkvalves, pressure limiters, purge circuits and likewise devices, etc. . ..

The output of the trailer relay valve 1 is coupled to a trailer brakevalve 5. The trailer brake valve 5 is coupled to a coupling device(trailer coupling head, not shown) for supplying air to a trailer(if/when coupled). The trailer relay valve 1 has an input denoted 11, anoutput denoted 12 and a supply AC4. The input is supplied by aproportional trailer control solenoid valve 4 having an input 41 and anoutput 42.

The trailer brake valve 5 is controlled by a line 50 coming out of theAPM, more precisely from the output of the trailer relay valve 1.

When line 50 is not under pressure (i.e. low pressure), the servicebrakes of the trailer are set. Conversely, when line 50 is underpressure (i.e. high pressure), the service brakes of the trailer areunset, and the wheels of the trailer can turn.

With reference to FIGS. 2A,5A,5B, there is arranged a switchoverauxiliary valve 2, interposed functionally between the trailer relayvalve 1 and the trailer brake valve 5. The switchover auxiliary valve 2is denoted in short ‘SwapV’ on the drawings.

The switchover auxiliary valve 2 is here pneumatically controlled by acontrol port 25 and has four input/output ports 21-24. The switchoverauxiliary valve 2 is a 4/2 type valve.

First port 21 is connected to the output 12 of the trailer relay valve1. Second port 22 is connected to the input 51 of the trailer brakevalve 5 via line 50. Third port 23 is connected to an outbound linecalled “pneumatic backup brake control line” BKC. Fourth port 24 isconnected to the air supply circuit AC4.

There is provided a movable plunger with two positions.

When the switchover auxiliary valve 2 is at rest (FIG. 5A), first andsecond ports 21,22 are in fluid communication, fourth port 24 is closed,third port 23 may be in communication with the atmosphere.

When the switchover auxiliary valve 2 is actuated under pressure fromcontrol port 25 (FIG. 5B), first and third ports 21,23 are in fluidcommunication, second and fourth ports 22,24 are in fluid communication.Under this condition the trailer brake valve 5 is controlled by the airsupply circuit AC4 (at somewhat constant pressure), and pneumatic backupbrake control line BKC is supplied by the controlled pressure deliveredby the trailer relay valve 1. We note that since the input 51 of thetrailer brake valve 5 is pressurized, the trailer is not braked throughthis line, but the trailer can still be braked properly by another line.

Stated otherwise, the output 12 of trailer relay valve 1 can beconnected selectively to the trailer brake valve 5 or to the pneumaticbackup brake control line BKC, upon control port 25 status.

There is provided a backup mode selection valve 3, controlled by thecontrol unit 61 of the production module 6. In the illustrated example,the backup mode selection valve 3 is an ON/OFF electro-valve, with apneumatic input 31 and a pneumatic output 32.

With reference to FIGS. 2A,5A,5B, the backup mode selection valve 3supplies the switchover auxiliary valve 2 via a Select Low valve 9. TheSelect Low valve 9 is of a known type, performing an overall ‘AND’function by selecting the lowest pressure available on its two inputs.

The pneumatic output 32 of the backup mode selection valve 3 isconnected to a first input port 91 of the select low valve 9. The otherinput port 92 of the select low valve 9 is connected to the second port22 of the switchover auxiliary valve 2. Said otherwise, the second inputport 92 of the select low valve 9 is connected to trailer supply line50.

The pneumatic output 93 of the select low valve 92 is connected to thecontrol port 25 of the switchover auxiliary valve 2.

The backup mode selection valve 3 is here a normally open valve.

Thanks to the low select valve 9, the switchover auxiliary valve 2 canonly be caused to be activated if, beforehand, both AC4 is supplied andthe trailer control solenoid valve 4 is controlled and the trailer relayvalve 1 delivers pressure at its output.

With reference to FIG. 2B, the backup mode selection valve 3 has itspneumatic output 32 connected directly to the pneumatic control port 25of the switchover auxiliary valve 2.

The backup mode selection valve 3 is here a normally closed valve. Inthis case, the control unit 61 operates with another appropriate logic.

Normal Brake Mode and Backup Brake Mode and Swap Therebetween

The brake system comprises a service brake electric input device 16(formed generally as a brake foot pedal) delivering a first inputelectric signal S16. The brake system comprises one or more electronicbrake control units (71,72,73) adapted to process the first inputelectric signal S16, and to deliver one or more electrical controlsignals (NBC,ES1,ES) to the front and rear axle brake modules FBM,RBM.

Depending on the level of autonomous drive capability, there may beprovided a conventional brake control unit 73, in charge of handlingelectric signal S16 from the brake foot pedal, and in charge ofdelivering a braking control signal (named here NBC for normal brakecontrol) to users such as FBM, RBM, trailer circuit.

Additionally, there may be provided autonomous drive control units71,72, as redundant units which work either in a parallel mode or in amaster/slave mode.

According to one example, electrical control signals delivered by firstautonomous drive control unit 71 are denoted ES1, electrical controlsignals delivered by second autonomous drive control unit 72 are denotedES2.

First and second autonomous drive control units 71,72, rely at least oncameras 75 which provides a flow of images S75 which are analyzed inautonomous drive control units 71,72. There may be provided other typeof sensors like radars, lidars, or the like inertial sensors, and alsocommunication data received from various traffic aware entities (fromfixed or mobile entities).

Each of the front and rear axle brake modules (FBM,RBM) is controlled bythe above mentioned electrical control signals (NBC and/or ES1 and/orES2) under a normal mode called “normal brake operating mode” NOM.

Whenever this normal mode is not fully operative, in particular from anelectrical problem, disruption/lack of electrical supply at theelectronic brake control units (71,72,73), from the perspective of atleast one of to the front and rear axle brake modules FBM,RBM, there isprovided in the system an alternative mode called backup brake operatingmode BKM.

Advantageously, each of the front and rear axle brake modules (FBM,RBM)can be controlled by a pneumatic backup brake control line BKC under thebackup brake operating mode BKM.

Since the brake foot pedal 16 is not configured to deliver pneumaticsignals, the inventors have found a way to use the existing trailerrelay valve 1 to fulfil the generation of an appropriate pneumaticbackup brake control line.

More precisely, under the normal brake operating mode NOM, the output 12of trailer relay valve 1 is connected to the trailer brake valve 5.

But whenever the backup brake operating mode BKM is necessary (i.e.under the backup brake operating mode BKM), the control unit 61 controlsthe backup mode selection valve 3 to open or close (respectively FIG.2A, 2B), the output of backup mode selection valve 3, if relevant viathe low select valve 9, controls pneumatically the switchover auxiliaryvalve 2, the latter changes to the actuated state (FIG. 5B), and theoutput 12 of trailer relay valve is connected to the pneumatic backupbrake control line BKC.

Therefore, with reference to the above description, under the normalbrake operating mode NOM, the output 12 of trailer relay valve 1 isconnected to the trailer brake valve 5 (trailer brake ‘interface’ asgeneric term), and under the backup brake operating mode BKM the output12 of trailer relay valve is connected to the pneumatic backup brakecontrol line BKC.

It should be noted that the pneumatic backup brake control line BKC isoutput and controlled by the air production module 6, independently ofthe brake control unit 73 and/or autonomous drive control units 71,72.

The control unit 61 of the APM 6 may take the decision to go to backupbrake operating mode BKM whenever it does not receive expected properelectrical signals from the other electronic control units. For examplethe control unit 61 of the APM 6 may expect to receive “I'm alive &healthy” signal from the brake control unit 73 and/or from one or moreof the autonomous drive control units 71,72, and in the case thosesignals are not properly received, control unit 61 of the APM 6 maycontrol the backup mode selection valve 3 so that the switchoverauxiliary valve 2 is switched to backup brake operating mode BKM.

Miscellaneous

On the relay valves (1,8), a back end loop circuit is provided with arestriction 68. This ensures stability of the pneumatic control anddiscards some inadvertent transients.

As shown in FIG. 6, in the braking system according to US standard,unlike the trailer brake valve already described above, there isprovided as trailer brake interface a tractor protection valve 5′. Inthis configuration the second port 22 of the switchover auxiliary valve2 is connected directly to the trailer coupling head—red hand—, and isalso connected to the control port of the tractor protection valve 5′.Thanks to this valve, the normal braking line TL-NBC is connected to thetrailer coupling head—blue hand—when pressure is supplied in theTL-Supply Line.

References 181,182,184 denote the internal pneumatic lines within theair production which respectively supply the parking brake relay valve8, the proportional park brake control solenoid valve 89, the trailerrelay valve 1, the proportional trailer control solenoid valve 4, thebackup mode selection valve 3.

The proportional park brake control solenoid valve 89 is controlled bycontrol unit 61 through line 69; the proportional trailer controlsolenoid valve 4 is controlled by control unit 61 through line 64; thebackup mode selection valve 3 is controlled by control unit 61 throughline 63.

The pneumatic brake system described above constitutes the main servicebrake system of the vehicle which is used to slow down and to stop thevehicle during normal operation, whatever the speed of the vehicle. Thepark brake system is used mainly to maintain the vehicle stopped when itis not in use. As discussed above, the park brake system can be leastpartly combined with the service brake system; nevertheless, a parkbrake system can be independent of the service brake system, it can forexample comprise a system for blocking the vehicle transmission.

Heavy-duty vehicles, such as trucks and buses, are also often equippedwith a deceleration system, which is only capable of slowing down avehicle, but often not capable of effectively stopping the vehiclecompletely within a reasonable distance. Such deceleration systems, suchas hydro-dynamic brakes or electro-dynamic brakes, are mostly efficientwhen the vehicle is riding above a certain speed. Such decelerationsystems are by essence different from the pneumatic brake systemdescribed above.

1. An electronically controlled pneumatic brake system for an automotivevehicle, the system being configured to operate either under a normalbrake operating mode or under a backup brake operating mode, the systemcomprising: at least one front axle brake module for providing pneumaticcontrol pressure to the left and right front pneumatic brake actuators;at least one rear axle brake module for providing pneumatic controlpressure to the left and right rear pneumatic brake actuators; a trailerbrake interface and a coupling device for supplying air to a trailer; anair production module selectively providing air under pressure to thefront and rear axle electronic brake modules via at least a first airsupply circuit and a second air supply circuit, and to a trailercircuit; at least two air reservoirs, respectively connected to firstand second air supply circuits; and a trailer relay valve, having anoutput, wherein: each of the front and rear axle brake modules iscontrolled by an electrical control signal under the normal brakeoperating mode and is controlled by a pneumatic backup brake controlline under the backup brake operating mode; and the output of thetrailer relay valve is connected to the trailer brake interface underthe normal brake operating mode, and the output of the trailer relayvalve is connected to the pneumatic backup brake control line under thebackup brake operating mode.
 2. The brake system of claim 1, comprisinga switchover auxiliary valve for connecting selectively the output ofthe trailer relay valve either to the trailer brake interface or to thepneumatic backup brake control line, depending on the current operatingmode, and controlled by at least a backup mode selection valve.
 3. Thebrake system of claim 2, wherein the switchover auxiliary valve is a 4/2valve with four ports and two plunger positions, with a pneumaticcontrol.
 4. The brake system of claim 2, wherein the backup modeselection valve is an ON/OFF electro-valve, with its output connected tothe pneumatic control port of the switchover auxiliary valve.
 5. Thebrake system of claim 2, further comprising a select low valve withoutput of the select low valve connected to the pneumatic control portof the switchover auxiliary valve.
 6. The brake system of claim 5,wherein one input port of the select low valve is supplied by the supplyline to trailer brake interface, and the other input port of the selectlow valve is supplied by the backup mode selection valve.
 7. The brakesystem of claim 6, wherein the backup mode selection valve is a normallyopen valve.
 8. The brake system of claim 7, wherein the backup modeselection valve is controlled by an air production module control unithoused in the air production module.
 9. The brake system of claim 1,further comprising a proportional trailer control solenoid valve, toprovide a control pressure to the trailer relay valve.
 10. The brakesystem of claim 1, further comprising: a service brake electric inputdevice delivering a first input electric signal; and at least oneelectronic brake control unit configured to process the first inputelectric signal, and to deliver electrical control signals towards thefront and rear axle brake modules.
 11. The brake system of claim 10,wherein the pneumatic backup brake control line is output and controlledby the air production module, independently of the brake control unitand/or autonomous drive control units.
 12. The brake system of claim 1,further comprising: a truck parking brake relay valve; a parking brakeelectric input device delivering a second input electric signal; and anair production module control unit adapted to process the second inputelectric signal, and to deliver control signals to a proportional parkbrake control solenoid valve, which provides a control pressure to theparking brake relay valve.
 13. The brake system of claim 1, wherein theswitchover auxiliary valve, the backup mode selection valve, andoptionally the select low valve are housed within the air productionmodule.
 14. The brake system of claim 1, wherein there is provided athird air supply circuit for providing a redundant pneumatic supply tothe front and rear axle brake modules.
 15. A vehicle comprising anelectronically controlled pneumatic brake system, the system beingconfigured to operate either under a normal brake operating mode orunder a backup brake operating mode, the system comprising: at least onefront axle brake module for providing pneumatic control pressure to theleft and right front pneumatic brake actuators; at least one rear axlebrake module for providing pneumatic control pressure to the left andright rear pneumatic brake actuators; a trailer brake interface and acoupling device for supplying air to a trailer; an air production moduleselectively providing air under pressure to the front and rear axleelectronic brake modules via at least a first air supply circuit and asecond air supply circuit, and to a trailer circuit; at least two airreservoirs, respectively connected to first and second air supplycircuits; and a trailer relay valve, having an output, wherein: each ofthe front and rear axle brake modules is controlled by an electricalcontrol signal under the normal brake operating mode and is controlledby a pneumatic backup brake control line under the backup brakeoperating mode; and the output of the trailer relay valve is connectedto the trailer brake interface under the normal brake operating mode,and the output of the trailer relay valve is connected to the pneumaticbackup brake control line under the backup brake operating mode.